<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .test{}
    #box{}

    #box p{}
  </style>
</head>
<body>
  <div class="test">123</div>
  <div class="test">456</div>
  <ul>
    <li>1</li>
    <li>2</li>
    <li>3</li>
  </ul>
  <script>
    // var list = document.getElementsByClassName('test')

    // console.log(list)

    // var list = document.querySelector('.test')  // 真实的 元素对象

    // console.log(123, list)
    // console.dir(list)

    // var list = document.querySelectorAll('.test')  // 伪数组
    // console.log(123, list)
    // console.dir(list)

    // console.log( document.body )  // body元素

    console.log( document.documentElement )  // html 元素
  </script>
</body>
</html>